[@Sedjwick]
At close range, yes even a small hand gun would penetrate.

However, if the windstorm inside was really strong, the aim would either be incredibly screwed, or slow them down enough for what you said to be the outcome. But that would need to be incredibly strong.

My understanding is that it is not that strong.

So, GM-logic ruling here.
The bullets pierce the van.

They won't be affected enough to matter in such a small area.

Sorry Sedj. Just basic bullet stuff.